pmundle said:
My PC is intel 845gvsr/40GB/512 MB/P4 2.8.OS is win XP. I have a
peculiar problem.When I start the PC , the CD ROM drive LED displays a
momentary blink, the cabinet LED shows a steady glow and the HDD LED
does'nt glow at all.Internally, a green LED glows on the
motherboard.The monitor remains blank.The power has to be switched off
from the UPS to make another starting attempt.Repeated attempts do not
help either.In this situation . I remove the RAM cards, and reinsert
them one by one.The next attempt normally is a successful one.The PC
works fine for a day or two.The initial problem repeats after that.My
RAM modules are 256 MB each but one is 333 Mz and the other one is 400
Mhz. On successful boot, the display shows 512 MB.The motherboard is
clean and devoid of dust.The RAM contacts are clean and do not have
any deposits.Please help me with your views.
http://www.intel.com/support/motherboards/desktop/d845gvsr/
http://downloadmirror.intel.com/15210/eng/D845GVSR_TechProdSpec.pdf
LED CR1F1, mentioned on page 40, could be what is glowing green.
And that tells you that +5VSB from the power supply is available.
The +5VSB should flow steadily, so that LED should never blink.
It you see blinking or glitching, it could be a power supply problem.
The symptoms look like the processor isn't starting. A possible
reason for that, would be the Vcore regulator shutting down right
after you start the machine. Some Vcore regulators have current limiting,
and if the ATX power supply is slow delivering full +12V, the Vcore
regulator can be tricked into thinking there is a problem. And it
can shut off. To "clear" a latched fault on Vcore, may require
removing all power from the system momentarily. So as long
as the green LED on the motherboard surface (CR1F1) is glowing,
chances are a latched fault can't be cleared.
It could also be that the Vcore regulator circuit on the motherboard
actually has a problem.
Using a PCI POST card, will give a quick indication of processor
activity. A card like this, is plugged into the PCI slot nearest the
processor. There is a two digit display, which will display numeric
codes. The BIOS code, writes to I/O port 80 while the BIOS is running.
Each time a new subroutine is entered by the BIOS, the display gets
updated. If you see a steady stream of flashing numbers, it means the
BIOS is doing its normal thing. If the display "sticks" at 0xFF or
0x00, generally that means the CPU wasn't able to start properly.
http://www.newegg.com/Product/Product.aspx?Item=N82E16815158065
A repair shop would probably swap power supplies for a quick test,
and if there were no change in symptoms, they'd tell you "it's your
motherboard".
Whether it is or not, I can't say.
If you removed the RAM, and got no error beep codes, then you'd know
it wasn't a RAM problem. If the CPU had always been working, you should
get some error beeps from the piezo speaker (item "Q" in the motherboard
diagram) on the motherboard, when the RAM is missing. If the RAM is
missing, and the CPU can't start and give beep codes, then that means
the CPU got stuck for some other reason. At this point, I'm assuming
Vcore latched off, but it is pretty hard to say for sure. It would be
nice, if some of these error conditions had visual indicators on the
motherboard (like latch-off), but they can't connect LEDs to everything.
I do not recommend using abrasives on gold plated RAM contacts.
For one thing, a person might not be using proper antistatic
precautions while doing so. The gold is very thin, and removing
it will leave the less-precious metals underneath, to make the
electrical contact. The metals underneath could oxidize easier,
and then you're on a slippery slope of "continuous cleaning".
I would sooner rely on the wiping action of the slot contacts,
than grind off the metal manually.
When removing or adding RAM, you should do that with the power
off. Don't add RAM when the green LED on the motherboard is glowing.
That is why they put the LED there - if the LED is glowing, it
isn't safe to make hardware changes inside the computer case.
Turn off the power and wait for the LED to go off, then change
RAM or other cards etc.
Paul